Tank for metal plating cylinders

ABSTRACT

An apparatus for use in electroplating a metal onto the surface of a cylinder having a shaft extending from either end thereof, said apparatus comprising a tank for containing electrolyte, a cylindrical sleeve resistant to attack by said electrolyte adapted from releasable fixed location of each shaft with one end thereof in leak-proof abutment with an end of said cylinder, each sleeve being of a length such that the total distances between the remote ends of the sleeves on said shafts is greater than the distance between a pair of opposite walls of said tank, each of size opposite walls of said tank having a recess in the upper edge thereof dimensioned to releasably accommodate the sleeves extending therethrough with the cylinder located during the electroplating, each recess being adapted to releasably receive dam means to close said recess such that the level of the electrolyte in said tank may be raised to completely immerse the cylinder during the electroplating, said dam means including mutually separable bottom and top members defining a circular opening dimensioned for alidable fit with the sleeve extending therethrough and anode means for containing said metal to be plated.

May 2, 1972 T. M. KANGAS TANK FOR METAL PLATING CYLINDERS 8Sheets-Sheet. l

Filed June 3, 1970 May 2, 1972 T. M. KANGAs TANK FOR METAL PLATINGcYLINmms 8 Sheets-Sheet a Filed Jne 3, 1970 May 2 72 I T. M. KANGAS3,560,255

TANK FOR METAL PLATING CYLINDERS Filed June s, 1970 e sheets-sheet zFIGB May 2 1972 T. M. KANGAs 3,660,265

TANK FOR METAL PLATING CYLINDERS Filed June 3, 1970 8 Sheets-Sheet 4.

FIG, 4

May 2, 1972 T. M. KANGAS 3,660,265

TANK FOR METAL PLATING CYLINDERS Filed June 3, 1970 8 Sheets-Sheet.

May 2 1972 T. M. KANGAS TANK FOR METAL lPLATING CYLINDERS Filed June3,1970

3 Sheets-Sheet 6 May 2, 1972 T. M. KANGAS 3,560,265

VTANK FOR METAL PLATING CYLINDERS Filed June 3, 1970 8 Sheets-Sheen 7May 2 1972 T. M. KANGAs 3,660,265

TANK FOR METAL PLATING CYLINDEHS Filed June 3, 1970 8 Sheets-Sheet. 8

8 HO ,f6 ,I8 ,I6 J

'-7- kl M js q i T\ FIS 5 \\\"f/// I8 lo FIG@ FIGIO United States Patent01 hcc U.S. Cl. 204-212 4 Claims ABSTRACT F THE DISCLOSURE An apparatusfor use in electroplating a metal onto the surface of a cylinder havinga shaf-t extending from either end thereof, said apparatus comprising :atank for containing electrolyte, a cylindrical sleeve resistant toattack by said electrolyte adapted for releasable fixed location on eachshaft with one end thereof in leak-proof abutment with an end of saidcylinder, each sleeve being of a length such that the total distancebetween the remote ends of the sleeves on said shafts is greater thanthe distance between a pair of opposite walls of said tank, each of saidopposite walls of said tank having a recess in the upper edge thereofdimensioned to releasably accommodate the sleeves extending therethroughwith the cylinder located for rotation in said tank to form the cathodeduring the electroplating, each recess being adapted to releasablyreceive dam means to close said recess such that the level of theelectrolyte in said tank may be raised to completely immerse thecylinder during the electroplating, said darn means including mutuallyseparable bottom and top members defining a circular opening dimensionedfor slidable tit with the sleeve extending therethrough and anode meansfor containing said metal to be plated.

The present invention relates to the electroplating of metals ontocylinders and in particular the present invention relates to an improvedapparatus for use in the electroplating of metals, such as copper, ontocylinders, in which apparatus the cylinders may, during electroplating,be completely immersed in the electrolyte.

The rotogravure process of printing requires a cylinder which isengraved by the intaglio method. In the preparation of such a cylinder,-a base cylinder which may be fabricated from cast iron, cast steel oraluminum, and is usually made from extruded steel tubing, iselectroplated with copper to produce on the cylinder a dense deposit ofcopper of fine grain structure in the form of a coating. The coppercoating is then etched with acid and the engraved cylinder so obtainedis finally chrome plated for protection against abrasion. Subsequent toits use in printing and for rc-use the etched surface is mechanicallyground down, suitably on a lathe or grinder, and the cylinder is thenreplated with copper, etched and chrome plated.

In the conventional copper plating of the cylinder, the cylinder isrotated in the electrolyte, which is usually a solution of coppersulphate and sulphuric acid with various additives therein, with theshafts extending from the ends of the cylinder by which the cylinder isaxially rotated extending through recesses in opposite walls of thecylinder to a drive mechanism. Spaced from and extending parallel to thecylinder on either side thereof in the electrolytic tank are copperanodes. These anodes can take the form of titanium baskets containingpieces of copper, which baskets are suspended from bus bars locatedabove the electrolytic tank. To reduce sludging of the anodic materialin the tank the baskets are usually surrounded by -iilter aid such as anelectrolyte resistant fabric, e.g. a polypropylene fabric. However, inorder to avoid corrosion of the shafts on either end of the cylinderwhich are usually made of steel or iron during elec- Patented May 2,1972 troplating, and because of the recesses in the walls of the tankthrough which the shafts extend, it has not heretofore been possiblewith such an apparatus to completely immerse the cylinder in theelectrolyte. Heretofore it has only been possible commercially dependingupon the diameter of the cylinder to immerse a maximum of about 30% ofthe curved surface of the cylinder in the electrolyte at any particulartime and the eiiiciency of the electroplating process is relativelypoor. It is found that with such apparatus to obtain the desired coppercoat on the cylinder for use in the rotogravure process of printing toeffect electroplating for a period of the order of '6 or more hours.

The present invention provides an apparatus for use in electroplating ofmetal onto the surface of a cylinder such as those useful in theaforesaid rotogravure process in which during the electroplating processthe cylinder to be electroplated may be completely immersed in theelec.- trolyte without subjecting the shafts of the cylinder tosignificant contact with the electrolyte with its attendant corrosionproblems and in which unacceptable substantial leakage of theelectrolyte from the tank is avoided. In particular, the presentinvention provides such an apparatus in which due to the completeimmersion of the cylinder in the electrolyte the time for electroplatinga given thickness of metal is substantially reduced. In particular forelectroplating copper the electroplating period may be reduced from aperiod of the order of 6 hours to about an hour to obtain a coppercoating sufficient for use in the rotogravure process of printing.

It has been found according to the present invention that when thestructure of the cylinder assembly is modified by releasably xedlylocating on each of the shafts a cylindrical sleeve formed from amaterial resistant to attack by electrolyte, e.g. polypropylene, withone end of the sleeve in leak-proof abutment with the end of thecylinder, Isuch that the total distance between the remote ends of thesleeves is greater than the distance between the pair of opposite wallsof the tank having the recesses and the recesses in the tank are of asize to releasably accommodate the sleeves which extend therethrough andwhen such recesses are closed by a dam means, which includes mutuallyseparable bottom and top members dening an opening dimensioned for aslidable lit with the sleeve extending through the recess, then it ispossible to raise -the level of the electrolyte in the tank to such anextent that the cylinder to be electroplated may be rotated in the tankin a completely submerged condition with the improved efficiency ofplating of the metal onto the cylinder in such a submerged condition.

The present invention also provides an improved apparatus which isadapted to accommodate any size of cylinder and maintain such cylinderin submerged condition during the electroplating process with thecommensurate improved eficiency in electroplating.

According to the present invention therefore there is provided anapparatus for use in electroplating a metal onto the surface of thecylinder having a shaft extending from either end thereof, saidapparatus comprising a tank for containing electrolyte, a cylindricalsleeve resistant to attack by said electrolyte adapted for releasableiixed location on each shaft with one end thereof in leakproof abutmentwith an end of said cylinder, each sleeve adapted to releasably receivedam means to close said recess such that the level of the electrolyte insaid tank may be raised to completely immerse the cylinder during theelectroplating, said dam means including mutually separable bottom andtop members defining an opening dimensioned for a slidable fit with thesleeve extending therethrough and anode means for containing said metalto be plated.

Thus, by providing an electrolyte-resistant sleeve on each of the shaftsextending from the cylinder and by providing a darn means whichaccording to a preferred embodiment of the present invention comprises apair of mutually separable plates which may be slidable into and out ofthe recess in the walls of the tank by means of channel members such asto provide a circular aperture therein dimensioned to have a slidablefit with the sleeve, there is minimum leakage of the electrolyte out ofthe tank due to the presence of the dam members in combination with thesleeve and there is minimal contact of the electrolyte with the shaft ofthe cylinder due to the protection provided by the electrolyte-resistantsleeve. In order to further reduce any leakage of electrolyte from .thetank through the dam means the sleeve is suitably provided on itsexterior surface with a ring which is also resistant to attack by theelectrolyte which is located and rotates in a channel formed in theedges of the plate members of the dam means forming the circularapertures.

It will be readily realized that in order to be fully effective thesleeve member and the dam means and the tank should be resistant toattack from the electrolyte in the tank to avoid unnecessaryr corrosionproblems and, as such, they are suitably formed of a natural orsynthetic resin having the aforesaid electrolyte resistance such aspolyolefin, e.g. polyethylene or polypropylene. For example a rubberlined steel tank may be used.

Cylinders for use in the rotogravure printing process usually come intwo forms namely, integral shafted cylinders which have shafts extendingtherefrom and sleeve type cylinders which do not have shafts extendingtherefrom. With the latter sleeve type cylinders in the process it isconventional to provide a shaft which extends completely therethroughIwith adjustable chucks thereon for locating the shafts and usuallythese shafts are sufficiently long to accommodate the cylindricalsleeves in accordance with the present invention. However, with integralshafted cylinders having shafts extending therefrom, in many cases theshafts are too short to accommodate the cylindrical sleeves in acordancewith the present invention, and, therefore, in order that the cylinderscan be electroplated in the apparatus of the present invention it may benecessary to releasably attach to the shafts, suitably by means ofbushings, extension shafts to provide the necessary length.

When operating the apparatus according to the present invention withcurrent densities similar to those used in the conventionalelectroplating apparatus, due to the large increase in surface areawhich is being velectroplated at any paricular time, i.e. the whole ofthe cylindrical surface area of the cylinder as opposed to at most 30%of it, the electrolyte is very quickly depleted and it has been founddesirable in order to maintain the concentration of the electrolyte torecirculate the electrolyte between the tank and a larger tank in whichthe electrolytic tank is suitably located during which recirculation theelectrolyte is replenished before return to the tank. Suitably pumpmeans are provided for pumping the electrolyte from the larger tank tothe electrolytic tank and the electrolyte returns to the larger tank byoverflow from the electrolytic tank. The pump means suitably includes afilter means for removing solid or foreign matter from the recirculatingelectrolyte.

While the present invention has been described primarily with respect tothe electroplating of copper onto a cylinder it will be readily realizedthat the apparatus of the present invention is applicable to anyelectroplating process where it is desired to electroplate a metal ontoa cylinder as for eiciency of operation it is always desirable that thecylinder be completely immersed in the electrolytic solution. Thus, forexample, the apparatus of the present invention may, with suitablemodification of the materials to allow for the electrolyte in theelectroplating process and the anodes, be used to chrome platecylinders.

The present invention Iwill be further illustrated by way of theaccompanying drawings in which:

FIG. 1 is a plan view of a copper electroplating apparatus according toa preferred embodiment of the present invention,

FIG. 2 is a section taken along the line 2-2 in FIG. 1,

FIG. 3 is a vertical section through an extension shaft for use in theapparatus of FIG. l,

FIG. 4 is a vertical section taken through a sleeve for use with theextension shaft of FIG. 3,

FIG. 5 is a top elevation of a shaft for use in electroplating sleevetype cylinders in the apparatus of FIG. l,

FIG. 6 is a top view of a sleeve for use with the shaft of FIIG. 5,

FIG. 7 is a detail of a clamp for fixedly releasably locating the sleeveof FIGS. 4 and 6 on the shafts of FIGS. 3 and 5, respectively,

FIG. 8 is a section taken along the line 8-8 of FIG. 7.

FIG. 9 is a detail of the dam means in FIG. 1, and

FIG. 10 is a section taken along the line 10-10 of FIG. 9.

Referring firstly to FIGS. 1 and 2, the apparatus comprises a tank 1formed or lined with an electrolyte resistive material such as rubber,located in a larger tank 2 by means of cross members 3 and brackets 4.Electrolyte is continuously by recirculated between the tanks 1 and 2 bymeans of a pump (not shown) which withdraws electrolyte from the tank 2through outlet conduit 5 and pumps it via a filter (not shown), whichremoves suspended solid matter from the recirculating electrolyte,through inlet conduits 6 to the tank 1. Electrolyte which has beensubstantially stripped of its components during the electrolysisoverflows from the tank 1 to the tank 2 where the electrolyte isreplenished with the components and in the tank 1 mixing of theelectrolyte is facilitated by means of air agitation pipes 7.

A cylinder 8 to be electroplated with copper is mounted for rotation inthe tank 1 on steel shafts 9 which extend through a recess 10 in thetank 2 and a recess 11 in the tank 1. Rotation of the cylinder 8 iseffected from a motor means (not shown) through the shaft 9. Each shaft9 has releasably fixedly mounted thereon a cylindrical sleeve 12 formedfrom an electrolyte resistant material such as polypropylene, the sleeve12 being maintained in position by a steel clamp 13 so as to form aliquid-tight seal with the end of the cylinder 8. Each recess 11 isclosed by a dam means generally indicated at 14 such that the sleeve 12extends through the dam means 14 whereby the cylinder 8 may becompletely submerged in the electrolyte in the tank 1 suitably by two orthree inches or even more during rotation thereof with a minimum ofleakage of the electrolyte through the dam means 14, i.e. through therecess 11.

Referring particularly to FIGS. l, 9 and 10, the dam means comprises abottom plate 15 and a top plate 16 formed of electrolyte-resistantmaterial, such as high density polypropylene, the plates 15 and 16 incombination defining a circular opening 17 dimensioned to accommodatethe sleeve 12 with a slidable fit. The plates 15 and 16 are located inposition on the ends of the tank 1, to close the recess 11, in channelshaped members 18 and plate members 19 which are also formed of highdensity polypropylene fixedly attached to the ends of the tank 1. Tofurther reduce leakage of the electrolyte between the sleeve 12 and theplates 15 and 16 through the opening 17, the sleeve 12 is provided witha ring 20 on its outer surface, suitably formed from polypropylene,which is accommodated in a recess 21 in the edges of the plates and 16dening the opening 17.. Each sleeve 12 (see FIGS. 4 and 6) has a recess22 in the surface thereof to allow for adjustment of the position of thering on the sleeve 12.

The cylinder 8 which may be electroplated in the apparatus of FIG. 1 maybe an integral shafted cylinder or a sleeve type cylinder. When thecylinder 8 is an integral shafted cylinder, it is quite common for theshaft integral with the cylinder 8 to be too small to accommodate thesleeve 12 and as such an extension shaft 23 (FIG. 3) may be releasablytxedly attached to the shaft of the cylinder 8 by means of a steelbushing 24. When the cylinder 8 is a sleeve type cylinder, for use inthe apparatus of FIG. 1, it is necessary to provide a removable shaft,such a shaft being for example that shown in FIG. 5 the shaft having axed cone 26 and an adjustable cone 27 which is fixedly releasablylocated in position by a lock nut 28. The cylindrical sleeve 12 suitablefor use with the extension shaft 23 is shown in FIG. 4 and thecylindrical sleeve 12 suitable for use with the shaft 25 is shown inFIG. 6. Both the sleeves 12 include a neoprene rubber sealing ring 29 onone end thereof for abutment with the cylinder -8 to form a leak-proofseal and a recess 30 at the opposite end thereof to accommodate aportion 34 of the clamp 13. The clamp 13 as shown in FIGS. 7 and 8comprises a pair of clampingmembers 31 and 32 which may be tightenedonto the shaft 23 or the shaft 25 by means of bolts 33 with the reducedportion 34 of the clamp being located in the recess in the sleeve 12.

Suspended from copper bus bars 35 extending longitudinally of the tank 1are titanium baskets 36 which contain pieces 37 of the metal, e.g.copper, to be plated onto the surface of the cylinder 8. The baskets 36are surrounded by fabric 38, suitably formed of an electrolyte resistantmaterial such as polypropylene, to reduce sludging in the tank 1. Powerconnections (not shown) are provided for supplying electricity to thecopper bus bars 35 and the shaft 9 whereby the cylinder forms thecathode and the titanium baskets form the anode in the electrolytic cellin the tank 1.

For use in the electroplating of chromium onto the cylinder theelectrolyte contains chromic acid which would attack polyethylene andpolypropylene and thus a chromic acid resistant material is used such aspolyvinyl chloride and further in chromium plating the anodes areconventionally lead and tin alloy anodes are used.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An apparatus for use in electroplating a metal onto the surface of acylinder having a pair of shafts, one extending from each end of saidcylinder, said apparatus comprising a tank having walls for containingelectrolyte, a pair of cylindrical sleeves resistant to attack by saidelectrolyte adapted for releasable fixed location on each shaft with oneend thereof in leak-proof abutment with an end of said cylinder, eachsleeve being of a length such that the total distance between the remoteends of the sleeve on said shafts is greater than the distance between apair of opposite walls of said tank, each of said opposite walls of saidtank having an upper edge and a recess in said upper edge dimensioned toreleasably accommodate the sleeves extending therethrough with thecylinder located for rotation in said tank to form the cathode duringthe electroplating, each recess being adapted to releasably receive dammeans to close said recess such that the level of the electrolyte insaid tank may be raised to completely immerse the cylinder during theelectroplating said dam means including mutually separable bottom andtop members defining a circular opening dimensioned for slideable t withthe sleeve extending therethrough and anode means for containing saidmetal to be plated.

2. An apparatus as claimed in claim 1 in which said dam means comprisesa bottom plate having a semicircular recess in one edge thereof anddimensioned to provide a slideable lit with the bottom half of eachrespective sleeve and a top plate having a semi-circular recess in oneedge thereof similar to the recess in the bottom member to provide aslideable iit with the top half of each respective sleeve, a ring memberbeing disposed around each respective sleeve and arranged on rotation ofsaid cylinder to rotate in a channel in the edge of said recesses insaid plate adjacent each respective sleeve.

3. An apparatus as claimed in claim 2 in which the recesses in saidwalls include channel members dimensioned to accommodate said platemembers for forming said dam means.

4. An apparatus as claimed in claim 3 in which said tank is located in alarger tank pump means being provided for circulation of electrolytefrom said larger tank to the electrolytic tank.

References Cited UNITED STATES PATENTS 2,155,392 4/1939 Ballard 204-25 X1,773,135 8/1930 Flanzer 204-212 X 1,133,059 3/1915 Perreur-Lloyd204-212 X 526,482 9/1894 Bridgman 204-212 390,991 10/1888 Stier 277-1302,124,108 7/1938 Grece 277-130 701,629 6/ 1902 Shallenberger 277-132878,328 2/1908 Arnold 277-130 678,529 7/1901 Timms 277-130 3,151,0489/1964 Conley et al 204-216 X JOHN H. MACK, IPrimary Examiner R. J. FAY,Assistant Examiner U.S. Cl. X.R.

